1. Field of the Invention
The present invention relates to a technology of reading an image from a two-sided document in an apparatus that includes a scanner apparatus.
2. Description of the Related Art
A copying machine, a scanner, a facsimile, or a multifunction peripheral that has functions of these devices alone includes an image reading apparatus for reading an image recorded on a sheet document, and the image reading apparatus has a document conveying mechanism for automatically conveying the document.
To read images recorded on both surfaces of the document by the image reading apparatus, there is available an image reading apparatus that automatically conveys the document by the document conveying mechanism included in the image reading apparatus to read the images from both surfaces of the document. Reading images from both surfaces of a plurality of documents by such an apparatus necessitates reversal of front and back surfaces of the documents by the document conveying mechanism. Hence, a bundle of documents discharged after the image reading may have front and back surfaces reversed, or an order from the first page to the last page may be reversed.
A document conveying mechanism of an image reading apparatus discussed in Japanese Patent Application Laid-Open No. 2004-043056 can solve such a problem. In the image reading apparatus discussed in Japanese Patent Application Laid-Open No. 2004-043056, a sheet feeding unit and a reading unit are coupled together on a reversal path, and a reversal unit (switchback unit) is disposed on the midway of the reversal path. The sheet feeding unit sequentially separates documents placed with front surfaces up from an upper side to convey the documents to the reversal path, and the reversal unit on the midway changes trailing edges to leading edges to return the documents to the reversal path. Back surfaces of the documents passed through the reversal path have become lower surfaces, and the reading unit reads images from the back surfaces.
The documents reversed at a sheet discharge unit after the reading are returned again to the reversal path. Front surfaces of the documents passed through the reversal path have become lower surfaces, and images are read from the front surfaces. The documents are then discharged to the sheet discharge unit with the front surfaces down. Thus, when two-sided documents of a plurality of pages are stacked from an upper side in order of pages, the documents are discharged from a lower side in order of pages.
When images are read from a plurality of documents, the plurality of documents are stacked on the sheet feeding unit. In a method discussed in Japanese Patent Application Laid-Open No. 2004-043056, when an operation of reading images from both surface of a document and discharging the document to the sheet discharge unit is repeated, a stacking order of the documents at the sheet feeding unit and a stacking order of the documents at the sheet discharge unit can be set similar. A speed of reading document images has a limit because of reading accuracy. Thus, by setting lower a document conveying speed at the reversal unit at the time of reversal, a period of time for a series of operations from feeding of the document through reading of images from both surfaces of the document to discharging of the document is shortened.
The image reading apparatus discussed in Japanese Patent Application Laid-Open No. 2004-043056 needs, in the document conveying mechanism, the reversal unit on the midway of the reversal path for guiding from the sheet feeding unit to the reading unit. The image reading apparatus also needs a path for returning the document reversed at the sheet discharge unit to the reversal path via the reversal unit.
In the case of one-sided reading, the document is directly conveyed from the sheet feeding unit to the reading unit. In the case of two-sided reading, however, the document is conveyed from the sheet feeding unit to the reversal unit. Hence, document conveying paths are different between the one-sided reading and the two-sided reading, thus necessitating a guide for conveying the document in a correct direction. A path from the reading unit to the sheet discharge unit and a path from the reading unit to the reversal unit are different from each other, thus necessitating separate inclusion of roller pairs for conveying the document to the respective paths. As a result, when all these components are installed, there is a problem of an increase in size of the image reading apparatus.